tools: update LICENSE and tools/icu/current_ver.dep

Update the LICENSE file and tools/icu/current_ver.dep file in order to
finalize the upgrade to ICU 64.2

PR-URL: https://github.com/nodejs/node/pull/27361
Fixes: https://github.com/nodejs/node/issues/26388


Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Steven R Loomis <srloomis@us.ibm.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>